1. Field of the Invention
The present invention relates to a data providing system such as, for example, a video-on-demand system.
2. Description of the Related Art
A conventional video-on-demand (VOD) system described by Nishio et al. in Japanese Patent Application Publication No. 07-322235 includes a plurality of video service nodes, a video gateway, and a video program transfer unit interconnected by a network, and in addition a service request monitoring unit and a reallocation planning unit.
The video service nodes have respective video storage facilities in which video programs can be stored. Some of the video service nodes may be connected to both video information providers and subscriber terminals; other video service nodes may be connected only to subscriber terminals.
The video information providers store and deliver video programs.
The video gateway provides access to a database storing a management table, referred to as a mapping table, that maps video program identification numbers to the identification numbers of the video information providers or video service nodes at which the video programs are stored.
The service request monitoring unit monitors service requests from the subscriber terminals through the video gateway, analyzes the requests, identifies video programs that are requested with high frequency, and identifies video programs with reduced request frequencies.
Based on the results of this analysis, the reallocation planning unit creates a reallocation plan specifying video programs that are to be deleted from their assigned storage locations or reassigned to new storage locations.
The video program transfer unit implements the reallocation plan created by the reallocation planning unit by deleting stored video programs from the storage facilities in the video information providers and video service nodes, transferring video programs to new storage locations in the video information providers and video service nodes, and notifying the video gateway of these change in the allocation of the video programs to the video information providers and video service nodes.
In this conventional VOD system, upon receiving a service request from a subscriber terminal, the video gateway refers to the management table in the database and notifies the corresponding video information provider or video service node of the title of the video program requested by the subscriber terminal. The video information provider or video service node that receives this notification transmits the video program with the specified title to the requesting subscriber terminal.
The service request monitoring unit accordingly monitors and analyzes service requests from the subscriber terminals and the reallocation planning unit decides which video programs to store in which video storage facilities in the network.
In this conventional VOD system, when a video information provider begins providing a new video program, the video program is initially stored only by the video information provider.
When the new video program is first requested from a subscriber terminal, the service request monitoring unit analyzes the request, the reallocation planning unit reallocates the program to the video service node to which the requesting terminal is connected, and the video program transfer unit transfers the video program in its entirety to that single video service node, to be stored in the storage facility of that video service node.
When new video programs are supplied in a steady stream, however, this method of assigning them to storage facilities purely on the basis of requests from subscriber terminals leads to an erratic distribution of storage locations, and inefficient sharing of the video program transmission load.